This invention relates to erodable agglomerates containing abrasive grains, and, more particularly to abrasive products containing the erodable agglomerates.
Conventional coated abrasives typically consist of a single layer of abrasive grain adhered to a backing. It has been found that only up to about 15% of the grains in the layer are actually utilized in removing any of the workpiece. It follows then that about 85% of the grains in the layer are wasted. Furthermore, the backing, one of the more expensive components of the coated abrasive, must also be disposed of before the end of its useful life.
To overcome this problem of waste, many attempts have been made to distribute the abrasive grains on the backing in such a manner so that a higher percentage of abrasive grains can be utilized, thus leading to extended life of the coated abrasive product. The extended life further leads to fewer belt or disc changes by the operators, thereby saving time and reducing labor costs. It is apparent that merely depositing a thick layer of abrasive grains on the backing will not solve the problem, because the grains lying below the topmost grains are not likely to be used.
The prior art describes several attempts to distribute abrasive grains in a coated abrasive in such a way as to prolong the life of the product. U.S. Pat. No. Re. 29,808 describes a grinding material comprising a multiplicity of hollow bodies whose walls contain abrasive grains and a bonding means for bonding the abrasive grains to each other at the wall surface, whereby during grinding a multiplicity of fresh abrasive grains become continuously available at the grinding surface wherein the grinding action of the grinding surface depends exclusively on the size of the abrasive grains.
U.S. Pat. No. 2,806,772 discloses an abrasive article consisting essentially of abrasive granules, a phenolic resin bond therefor, and thin walled hollow spheres less than 0.025 inch in diameter distributed throughout the resin bond and between the abrasive granules. The spheres constitute 1 to 30% of the volume of the article.
U.S. Pat. No. 4,311,489 describes a coated abrasive product having abrasive particles secured to a backing by maker and size coats where each abrasive particle consists of an essentially solid agglomerate of fine abrasive grains and an inorganic, brittle cryolite matrix. The agglomerates have an irregular surface which permits a strong bond to the maker and size coats which permits gradual wearing down of the agglomerates during grinding by gradual removal of dulled abrasive grains from the agglomerates.
German Auslegeschrift No. 2,417,196 describes a coated abrasive article comprising an abrasive body on a substrate. The abrasive body comprises a hollow body, the walls of which are formed of binder and abrasive grain. The hollow bodies are ruptured during the grinding process, thus allowing the wall of the hollow body to act on the material being abraded. Accordingly, grain wear is distributed over the entire surface area of the substrate. Although the products described in those patents are useful, even greater utilization of abrasive grains in coated abrasives is desired by industry.